You need to change the editor for the
text/plain mime type or
public.plain-text UTI. The regular Get Info dialog changes the association for the file name extension, which these files don't have.
Get RCDefaultApp and install it.
Open System Preferences » Default Apps » Apps. Select your desired default editor, and look for either of the above in the application's list of supported types.
Select the entry, and click Set as Default. You're done. Both opening from Finder and the command-line
open will open your new default editor.
This also changes all
.txt files and the like. I don't think this can be prevented, since OS X thinks both these and extension-less files are
To do this without RCDefaultApp, edit Edit
Add an entry under
LSHandlers, containing the UTI (key
public.plain-text) and application bundle identifier (
It looks like this in Property List Editor: